The invention relates to a lock assembly adapted to be disposed on a locker or cabinet door adjacent to a flange surrounding an opening in said cabinet, comprising, on the one hand, a rotary operating member accessible from the exterior of the door and rotatably mounted in a body integral with said door about an axis orthogonal to the plane thereof and, on the other hand, an inner movable bolt which is associated to said operating member and to a return or compression spring which biases it towards an inoperative position, said bolt being provided with an inclined ramp adapted to cooperate with said flange so that said bolt first is moved backwards while compressing said spring whenever a force is applied to said door in a direction tending to close it, and then is moved in the opposite direction and is thus engaged under said flange, whereby the lock can be opened only by inserting either a key or a tool into said operating member.